But the Wash is in the Swamp or the Cesspool, depending on your love of DC and knowledge that it was indeed built on swampy marshland. Don’t want to know what your Bal’s could catch being too close to that Wash.
DC is of course also “The Nation’s Capital”
And for a not-so-proud distinction, the entire Ball-Wash is the nation’s syphilis capital:
Buffalo and Niagara Falls New York are collectively known as the Niagara Frontier.
If you include all 8 counties it’s often called Western New York. Or as I put it, as far away from the city as I can possibily get and stay in the same state without falling into a lake.
The whole middle swath of the state is commonly known as the fingerlakes region.
While this maybe true for certain Queen Cities, it does not hold true for the Queen City that is Charlotte, NC. Charlotte, NC was named for Queen Charlotte, the wife of England’s King George and the county that Charlotte is in was named for Mecklenburg, Queen Charlotte’s home state in Germany.
When I lived there, we would lovingly refer to the southeastern Massachusetts-Rhode Island area as the “armpit of the Cape”.
Montreal doesn’t have much in the way of nicknames that anyone really uses, but Quebec City is la vieille capitale (the old capital) or le gros village (the big village).
Ottawa is Bytown (a former name) and Toronto is Toronto the Good, Hogtown, The Big Smoke, la ville-reine (the queen city), or T.O.
What’s the deal with the statue where she looks like she’s been kicked in the gut?
(BTW, Charlottetown, PEI and the Queen Charlotte Islands in BC were named for the same queen.)
You forgot “The Armpit of the Midwest” 
Seriously, however, Detroit’s southern suburbs are referred to as Downriver.
D.C. is unofficially known as “Chocolate City.”
My area is called the “Mid-Hudson” (the area between NYC and Albany) or sometimes the “Tri-State Region” (which throws in parts on New Jersey and Connecticutt). Or if you’re from NYC, you call it “upstate” and ignore the fact that it’s actually in the lower half of the state.
I used to live in Elmira, which was part of the “Southern Tier” - the area of New York which ran along the Pennsylvanian border from Jamestown to Binghamton.
Tupelo, Mississippi in no way qualifies as a “metro area”.
But if pressed, I’d say either “The Birthplace of the King”, or “The Bible Belt Buckle”.
I miss Chicago.
Houston is also known as H-town.
(I never hear Space City, I think that one might be dying out as the glory days of Nasa and the space race are long past.)
And I thought it was Valley of the Meth Lab…
I don’t think you could call my city, Starkville, Mississippi a metro area, but it is often called Starkvegas. Sarcastically of course, because of its lack of nightlife.
We’re also in the “Treasure Valley.”
The Twin Falls, ID area is the “Magic Valley.”
neuroman is correct that “Space City” is an artifact of the '60s, and not in much common usage anymore. But there are still plenty of small businesses here named “Space City Xxxxx.”
You guys have got places with people of imagination, so it seems. Auckland is just “The Big Smoke”, “Above the Bombays” (The Bombays are the Bombay Hills just to the south of here), “City of Sails”, “The Queen City” (although that one is not used as often these days.)
DJs and such will often refer to Jackson, MS as “Jacktown”.
Las Vegas:
Local weather forecasters call it the Vegas Valley.
Locals generally call it Las Vegas, but “Vegas” is not an insult.
“Sin City” is a compliment.
“Lost Wages” an old joke (no offense to our SDMB poster with similar name).
But please, don’t do your Austin Powers “Vegas Baby” unless you are Mike Myers.
Along the same lines, because of the Marshall Space Flight Center, Huntsville, Alabama is sometimes known as “Rocket City.”
We’re quite presumptuous here in The Bay Area. As has already been noted in this thread, the San Francisco Bay is the only bay that counts as The Bay Area. San Francisco itself is referred to as The City. The only actual city, y’know? And I live on The Peninsula, which thrusts into the Pacific Ocean like some mighty boner, with The City at its throbbing tip.